The Collaborative International Dictionary of English v.0.48:
Tap \Tap\, n. [AS. t[ae]ppa, akin to D. tap, G. zapfen, OHG.
zapfo, Dan. tap, Sw. tapp, Icel. tappi. Cf. Tampion,
1. A hole or pipe through which liquor is drawn.
2. A plug or spile for stopping a hole pierced in a cask, or
the like; a faucet.
3. Liquor drawn through a tap; hence, a certain kind or
quality of liquor; as, a liquor of the same tap. [Colloq.]
4. A place where liquor is drawn for drinking; a taproom; a
5. (Mech.) A tool for forming an internal screw, as in a nut,
consisting of a hardened steel male screw grooved
longitudinally so as to have cutting edges.
(a) Ready to be drawn; as, ale on tap.
(b) Broached, or furnished with a tap; as, a barrel on
Plug tap (Mech.), a screw-cutting tap with a slightly
Tap bolt, a bolt with a head on one end and a thread on the
other end, to be screwed into some fixed part, instead of
passing through the part and receiving a nut. See Illust.
Tap cinder (Metal.), the slag of a puddling furnace.